Final full-text version of this paper available at: http://dx.doi.org/10.1038/375654a0Anterior–posterior polarity in Drosophila arises from the movement of the oocyte to the posterior of the egg chamber, and the subsequent acquisition of posterior fate by the adjacent somatic follicle cells. We demonstrate that gurken is necessary in the oocyte and torpedo/DER in the follicle cells for the induction of posterior fate. As the gurken–torpedo/DER pathway also establishes dorsoventral polarity later in oogenesis, Drosophila uses the same germline to same signalling pathway to determine both embryonic axes.A.G.-R. was a European Molecular Biology Organisation postdoctoral fellow. This work was supported by a Wellcome Trust Senior Fellowship (D.StJ.) and a European Community Postdoctoral Fellowship (A.G.-R.)Peer reviewed